Edmond Chow

Ultracompact biochemical sensor built with two-dimensional photonic crystal microcavity

By measuring the resonant wavelength of a two-dimensional photonic crystal microcavity, we can detect the change in refractive index of 0.002. Evaporative process of water in 5% glycerol is used to demonstrate time-resolved sensing capability

Direct measurement of the quality factor in a two-dimensional photonic-crystal microcavity

A new microcavity design is proposed and structures are realized with a two-dimensional photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q value of 816+/-30 is achieved at lambda =1.55 mum . This high- Q cavity will permit the realistic realization of spontaneous-emission modification and on-off optical switches.

Toward, single molecule detection with photonic crystal microcavity biosensors

Time resolved biomolecular binding events were measured using photonic crystal microcavity resonators integrated with microfluidics. The optical field is confined to a volume of 33 times 10-18 liters, which enables monitoring of single binding events

Controlled formation of individually seeded, electrically addressable silicon nanowire arrays for device integration

The formation of large-scale arrays of individually seeded, electrically addressable Si nanowires with controlled dimension, placement, and orientation is demonstrated. Electron beam evaporated gold nanoparticles were used for nanowire synthesis. By controlling the lithography and metal deposition conditions, nanowire arrays with narrow size distributions have been achieved. Low-energy postgrowth ion beam treatment has been utilized to control the orientation of Si nanowires. This process also leads to the attachment of nanowires on the substrate. Fabrication of planar devices with robust metal contact formation becomes feasible. The method enables efficient and economical integration of nanowires into device architectures for various applications.

Demonstration of high waveguide bending efficiency (>90%) in a photonic-crystal slab at 1.5-μm wavelengths

Using a 2D photonic-crystal slab structure, we have demonstrated a strong 2D photonic band gap with the capability of fully controlling light in all three dimensions. Our demonstration confirms the predictions on the possibility of achieving 3D light control using 2D band gaps, with strong index guiding providing control in the third dimension, and raise the prospect of being able to realize novel photonic-crystal devices. Based on such slab structure with triangular lattice of holes, a 60 degree photonic-crystal waveguide bend is fabricated. The intrinsic bending efficiency is measured within the photonic band gap. As high as 90 percent bending efficiency is observed at some frequencies.

Micro-fabrication and Nano-fabrication of Photonic Crystals

For the past decade, the operating wavelength λ of photonic crystal structures has progressed rapidly from millimeter waves to infrared and even to optical wavelengths of λ= 400nm − 1,500 nm [1–8]. The fabrication methos has also evolved dramatically. It started from the early mechanical drilling of dielectric holes to the most recent micro- and nano-fabrication of dielectric materials using either lithographical [8–9] or chemical methods [10–11]. In this article, I intend to give an overview of photonic crystal structures created using advanced semiconductor processing techniques.

Transmission measurement of quality factor in two-dimensional photonic-crystal microcavity

A new micro-cavity design is proposed and structures are realized using a 2D photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q-value of 816+/- 30 is achieved at (lambda) =1.55micrometers . This high-Q cavity will enable realistic realization of spontaneous emission modification and on-off optical switches.

Photonic bandgap waveguides-2D PBG materials embedded in a GaAs-AlO slab

A new two-dimensional photonic crystal (2D PC) slab structure was created with a full three-dimensional light confinement. Guided modes with broad bandwidth and high transmission for such PC waveguides and bends are also observed.

Fully confined photonic band gap and guided modes in a two-dimensional photonic crystal slab

Summary form only given. As an optical analog to electronic crystals, the photonic crystal (PC) promises a revolution in the photonic world similar to the electronic revolution created by the electronic band gap engineering in semiconductors. A two-dimensional PC has the advantage of being easier to fabricate at optical wavelength (/spl lambda/) compared with a 3D PC. However, the light leakage in the vertical direction has been the main problem for using a 2D PC in opto-electronic application. In the study, we solve this problem by combining a traditional 2D PC with a strong vertical index guiding between the waveguide layer (GaAs) and the cladding layer (Al/sub x/O/sub y/).

Applications of photonic crystals in optoelectronics

In this paper, I describe realistic applications of photonic band gap (PBG) materials in optoelectronics at the mm-wave, IR and optical wavelength regimes. Examples are highly dispersive PBG-prisms and PBG-lasers. I will also describe our recent breakthrough at Sandia in the successful fabrication of 3D silicon photonic crystal operating at IR wavelengths.